Observations of galaxies, galaxy clusters, distant
supernovae, and the cosmic microwave background radiation tell us that ~85% of
the matter in the universe is comprised of one or more species of dark
matter.With the continuing success of
the Standard Model of particle physics, the existence of dark matter provides
one of the few tangible sign posts as we seek to understand what lies beyond
the Standard Model.Deciphering the
nature of this dark matter would be of fundamental importance to cosmology,
astrophysics, and high-energy particle physics.

A leading hypothesis is that dark matter is comprised of
particles that were produced moments after the Big Bang.The Cryogenic Dark Matter Search (CDMS) is
one of several experiments underway to directly detect these particles and
begin an era of dark matter science that will hopefully allow us to understand
the nature of the dark matter.

The CDMS experiment
has pioneered the use of cryogenic silicon and germanium detectors to perform
sensitive searches for dark matter.The recoiling nucleus from a dark matter interaction produces crystal
lattice vibrations (phonons) and also electron-hole pairs (left).The phonon and charge signals are captured
by electrodes applied to the face of the crystal using photolithography
(right).These detectors provide
unique capabilities for background rejection and offer unmatched sensitivity
for the very small energy deposits associated with low-mass dark matter
interactions.

The SLAC
CDMS group participates in the operation and data analysis for the SuperCDMS
Soudan experiment installed in the Soudan Underground Laboratory.The experiment resides in a former iron
mine in northern Minnesota at 2340’ below ground to shield the experiment
from cosmic ray backgrounds.Detector
towers are installed into a cryostat that allows them to be cooled to 0.05
degrees Kelvin above absolute zero in order to detect the phonon signal
(left).The SuperCDMS Soudan
experiment is currently running with five towers (15 detectors) providing a
target mass of 9 kg of germanium (right).Results from the experiment are the most sensitive to date for dark
matter masses below 6 GeV.

The SLAC CDMS group is deeply engaged in the proposed SuperCDMS SNOLAB
experiment to be located 6800’ below ground at the SNOLAB underground science
laboratory near Sudbury, Canada.SuperCDMS
SNOLAB utilizes larger detectors in a versatile cryostat with an initial
payload of 100 kg of germanium and 10 kg of silicon detectors (left).The SLAC group has overall responsibility
for the detector payload (detectors and associated cryogenic mechanics and
electronics) and offline computing for the experiment.SuperCDMS SNOLAB is one of the proposed
“Generation 2” dark matter experiments that seek to push the sensitivity for
observing dark matter to the “neutrino floor” where neutrino backgrounds
begin to contribute (right).SuperCDMS
SNOLAB is also expected to make the first measurement of coherent neutrino
scattering of the 8B neutrinos from the sun.